In the processing of corn germ, there is produced a wet-milled corn germ which has a high moisture content, for example, between 50% and 55% moisture, and it is necessary to reduce this moisture content down to a substantially lower value, for example, between 2% and 3%. Commonly, the moisture reduction is accomplished in a series of three or more rotary horizontal cylinders or drums each of which has a diameter of about 10 to 13 feet, a length of about 60 to 80 feet and encloses axially extending steam tubes. Each rotary drum also has internal vanes and is supported with its axis on a slight incline. Wet-milled corn germ material and heated air are fed or directed into the slightly higher end of the rotating drum, and internal vanes progressively feed the material axially through the drum and shower the material over the steam tubes for heating the material and evaporating the moisture.
The drier corn germ material exits from the opposite end of each rotating drum along with the moisture laden hot exhaust air, and large diameter rotary seals are required for both ends of the rotating dryer drum. As a result of the large diameter of the rotary seals and the necessary clearance for the rotating elements, it is difficult to prevent the moisture laden hot air from escaping into the atmosphere and to prevent leakage of the corn germ material, especially from the discharge end of the rotary drum. This hot gas or air leakage and the heat loss from the rotary drum result in a relatively low recovery of energy from each dryer unit, for example, on the order of a 65% energy recovery. The leakage of the moisture laden hot air from the discharge end of each rotary drum dryer also results in the escape of objectionable odors into the atmosphere since the dryers are usually located outside of a building.